When settling on a territory or when nest relocation becomes necessary, it is important for any organism to efficiently evaluate potential nest sites in order to choose the one most suitable under current conditions.  However, if time is limiting, species may experience a speed-versus-accuracy trade-off when searching for a new home.  We examined nest site selection under duress (in the form of flooding) in two species of ants, Linepithema humile and Tapinoma sessile.  Flooded colonies were presented with new nest chambers that were either higher, lower, or at the same elevation as their current nest.  We also tested if their ability to efficiently choose a new site was influenced by the rate of flooding.  If ants are able to assess and evacuate to the most suitable location, then ant colonies should move to a higher elevation relative to their current nest site in response to flooding.  However, their ability to do so efficiently may be compromised if they do not have enough time to assess the relative quality of available nest sites.

Results/Conclusions

We found that both species moved their nests to the higher nest chamber when faced with rising flood waters.  Moreover, both species always moved their entire nest to the same chamber.  However, when the drip rate was doubled, ants were less likely to move into the higher nest and T. sessile was more likely to split their nests into two of the available chambers.  These results provide a framework for future opportunities to study evacuation response and ant colony adaptability to disturbance.